The greenhouse effect of CO2 has been recently pointed out as one factor of the global warming phenomenon and it has become an international urgent issue to take measures in preserving earth environments. All fields of human activities that involve burning of fossil fuels are CO2 generation sources, and needs for CO2 emission limitation are becoming increasingly great. Accordingly, methods that enable to bring flue gas of a boiler into contact with an amine CO2 absorbent to reduce or recover CO2 in the flue gas, and methods that enable to store recovered CO2 without releasing CO2 to the atmosphere have been intensively studied for power-generating facilities such as thermal power plants that use a large amount of fossil fuels. As steps that enable to reduce or recover CO2 from flue gas by using a CO2 absorbent as described above, a step of bringing flue gas into contact with a CO2 absorbent in an absorber and a carbon dioxide recovery system that heats an absorbent having absorbed CO2 in a regenerator to liberate CO2 as well as regenerates the absorbent and circulates the regenerated absorbent again in the regenerator to reuse the absorbent are adopted.
This carbon dioxide recovery system causes carbon dioxide contained in gas in the absorber to be absorbed by the absorbent and then be heated in the regenerator, thereby separating the carbon dioxide from the absorbent, so that the separated carbon dioxide is separately recovered and a regenerated absorbent is cyclically used again in the absorber.
To separate and recover carbon dioxide in the regenerator, the absorbent needs to be heated by a regenerating superheater and heating steam at a prescribed pressure needs to be supplied thereto. When CO2 is to be recovered from flue gas of a practical power plant, a large amount of steam is required to regenerate the absorbent.
To supply the steam, methods that enable to bleed steam from a steam turbine of a power generation system, that enable to bleed steam from each header between a high-pressure turbine (HP) and an intermediate-pressure turbine (MP) or between an intermediate-pressure turbine (MP) and a low-pressure turbine (LP), or that enable to recover power from bled steam using a steam turbine and supply emission to a regenerating superheater in a CO2 recovery system have been proposed (see Japanese Patent Application Laid-open No. 2004-323339).